Rotary wing (RW) nap-of-the-earth (NOE) flight requires two major skills: superior aircraft control and specialized map interpretation and pilotage. U.S. Army training in the latter is to be accomplished via the Map Interpretation and Terrain Analysis Course (MITAC). This course of instruction presently lacks an instrument for measuring comprehension of the concepts and principles taught in it. In evaluating a potential achievement test, 115 items were administered to 182 initial entry RW students, and a subset of 49 highly reliable items was identified. Students' scores on this subset were validated against their performance 6 weeks subsequent as NOE navigators. Test reliability and validity are discussed in detail.